


Moche Monsters

by themegalosaurus



Category: Supernatural
Genre: Alternate Universe - Canon, Angst and Humor, Case Fic, Gen, Men of Letters Bunker
Language: English
Status: Completed
Published: 2014-10-23
Updated: 2014-10-23
Packaged: 2018-02-22 06:01:32
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 9,188
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2497169
Author URL: https://archiveofourown.org/users/themegalosaurus/pseuds/themegalosaurus
Summary: <blockquote class="userstuff">
              <p>In which Castiel gets a guinea pig.</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

  * For [outpastthemoat](https://archiveofourown.org/users/outpastthemoat/gifts).



> Written for the SPN Summergen fanfic challenge to a prompt from outpastthemoat. Set post-9x03 in a verrry slight AU where Cas didn't leave the bunker at the end of the episode.

Sam could feel himself falling asleep. The familiar smell of the Impala’s interior and the warm rumble of her engine through the seat were irresistibly soothing in his worn-out state. Dean was right: the trials were still singing through his system, keeping his body humming a little too hot and draining his energy much faster than he’d learned to expect. The three-mile run he’d taken that morning ought to have been nothing – would have been nothing, six months ago. But now it was weighing heavy on his eyelids and in his limbs.

“ _Castiel!”_

Dean’s outraged tones cut through the dark of Sam’s doze. He twitched awake, blinking across the front seat to where his brother twisted around, angling angrily toward the angel – former angel – riding in back.

“That had _better not_ be a goddamn _guinea pig_ in your pocket.”

Sam glanced up at the rear-view mirror, to see Castiel rearrange his features into an unconvincing approximation of innocence. A tell-tale bulge was evident at his side, squirming fat under the fabric of his coat. Of course, Muriel was along for the ride. Cas had been inseparable from his pet ever since Dean had bought her, in an uncharacteristic gesture Sam supposed had something to do with Castiel’s momentary death back in Emory Park. It certainly didn’t reflect an interest in domestic rodents. Over the six weeks that Cas had been back at the bunker, the relationship between Dean and Muriel had become increasingly strained.

“I don’t know, Dean,” Sam said now, hoping to head off the argument. “What would you rather he had wriggling around in there?”

“We discussed this!” Dean said. “No pets in the Impala!”

Huh. Apparently Dean was too pissed to bite, even with the juicy carrot of sexual innuendo being dangled before him. Sam would have to take one for the team.

“Strictly speaking,” he began, “I thought the rule was no dogs” - but Castiel spoke over him, putting up a determined defence.

“Muriel is not a _pet_ , Dean. She is a companion and a friend. I would never advise you to leave Sam behind on a hunt.”

“Cas?” said Sam. “I’m team Muriel right now but if you carry on that line of argument you might find my sympathy waning.”

Dean raised an eyebrow; but even Sam’s sudden demotion wasn’t enough to deflect his annoyance. “I swear to god, Castiel,” he muttered, “if you still had your wings you and that oversized hamster would be back at the bunker _right now_.”

“As convenient as that would be,” said Sam, “we’re all limited to ground transportation. And we can’t let eight hours of driving go to waste. What’s the worst that can happen? It’ll be fine.”

“Yes, Dean,” Castiel chipped in. “Your negative attitude is quite unnecessary. I’m certain Muriel will make a valuable contribution.”

“Sure,” Dean said, “Just like she did last time, when that sandwich shop guy turned out to be allergic and started sneezing right in the middle of our stakeout. Or maybe like the time before, when you lost her in that medical museum. Six hours,Cas, _six hours,_ in an exhibit on diseases of the lower bowel. Or perhaps, and don’t think I forgot this, it’ll be like the time before _that,_ when –”

“That’s unkind,” said Castiel. “All of us have made mistakes.”

“Sure,” said Dean. “Sam and I have done all kinds of shit. But unless Sammy isn’t telling me something significant, neither of us has ever peed on a priceless Egyptian papyrus.”

~*~*~*~*~*~*~

“I told you,” Castiel said. “I knew Muriel would prove invaluable.”

Sam had to hand it to him: just this once, he’d been right. The kid who’d been the only witness to her neighbour’s late-night disappearance had stubbornly failed to respond to Dean’s friendly approaches, clutching her mother’s skirt and backing away in silent refusal when he tried to prise out of her the details of what she’d seen. Dean had always been more confident dealing with children; but noticing the strain in his tone and his smile, Sam had reluctantly braced himself to tag in. Luckily, Muriel had chosen that moment to poke a pink nose over the rim of Castiel’s pocket.

The little girl, Keira’s, face had transformed as soon as she saw her. She cracked a gap-toothed smile and stuck two sticky palms out to Cas – who (wonder of wonders) had actually ponied up, releasing the guinea pig reluctantly into her grasp. Clutching Muriel, Keira had started to talk: describing the curving claws and the burnt-ash scent of the thing that had scared her (“it smelled like a campfire”, she’d said). More than that, she’d witnessed its transition to a human form: confirming that the beast they were hunting didn’t look like a beast all the time.

This kind of detail was exactly what Sam had been hoping for. He might not, yet, be completely sure what they were dealing with; but he was definitely on the way to figuring it out. He could almost feel the pages turning in the back of his mind, flickering back through a lifetime’s research for the shape of the thing that they sought. The effects of the trials had been more than just physical. His body might be creaking under their strain, but his mind was still running unusually fast, his memories unnaturally clear.

“Whaddya think, Sammy?” asked Dean as they got back to the car.

“About Muriel? She did a good job. Professional.”

“No, you dork. What do you think about the case? We still looking at a, what was it, a sprite?”

“After that? I'm not so sure. Sprites are primarily water creatures and Keira’s thing about the burning smell probably rules that out. But I have some ideas. Really, I’m just pleased that she finally spoke to us.”

“Yeah, tell me about it. Guess the guinea pig’s good for something.”

Sam smiled. “She has better people skills than Cas.”

~*~*~*~*~*~*~

Flipping through the pages of the Encyclopedia of American Folklore (it was amazing what you could find in these small-town libraries), Sam paused – then froze – as the threads pulled together. He’d been right, yesterday – it definitely wasn’t a sprite. It was a cherufe. Which alsomeant it wasn’t a woman, but a man. That put paid to their already short list of suspects – and _that_ , Sam realised, already standing to leave, meant that the innocent-looking tree surgeon Dean and Cas had just gone to interview was almost certainly the very big bad they were trying to hunt. Great. Dean probably hadn’t taken anything but his gun, not into the house at least, and the all-new humanoid Cas couldn’t even shoot straight. Sam had to get over there, right away.

Heading out into the library parking lot, Sam swung around to recce the available vehicles. There was a brand new silver BMW that would definitely get him there quickly; but new cars like that tended to have fancy alarms, and complicated locking systems that would cost him valuable time. No, the beat-up Ford pickup over in the corner might not run as smoothly but it would be a hell of a lot faster to crack. He’d barely finished the thought before he was wiggling a blade down the side of the driver’s door, prising it open and sliding in behind the wheel.

Jumping stop signs and red lights all the way across town, he made it to Abraham’s house in fifteen minutes; pulling the truck to a noisy halt in the empty street outside. As he paused to contemplate his best choice of cover story – his jeans and flannel shirt didn’t really scream ‘FBI’ - an unholy screech echoed out of an upstairs window.

“Jesus!” Too panicked for caution, Sam threw himself out of the car, sprinting across the lawn and up the porch to crash open the front door with a kick. “Dean!” he called out, raising his gun.

He was surprised to see his brother come hurrying down the stairs, obviously perturbed but still too neat to have been in a fight. “Sammy? What are you doing here?”

“Came to warn you - cherufe,” Sam panted. Stopping so suddenly, adrenalin draining, a now-familiar dizziness surged through him. He bent over, hands on knees, and blinked up at Dean through the strands of his hair. “I was worried you guys had walked into a trap but now I feel like a jackass. Did I make a mistake?”

“No, dude,” Dean said. “You were totally right. You OK?”

“Yeah, yeah, I’m fine. Sorry. Just give me a second. What happened? Is he out? Is he gonna come back?”

“He’s definitely not coming back from where he’s gone. Up here, take a look.”

Swatting away Dean’s hovering arm, Sam followed his brother upstairs to the first floor landing, heading along the hallway to a peach-papered master bedroom. Everything was pale and tasteful and undisturbed; except for the tableau directly in front of the door, where a rust-red bloodstain blotted the heavy cream carpet. As Sam stared, the edges of the stain crept slowly outward, fed by a slow, sticky pulsing of fluid from the neatly severed neck of the body at its centre. Dean was right. Abraham was no longer a threat.

“Did you do this?” Sam asked. The kill seemed excessive, when cherufe could be most efficiently despatched with a stab to the heart. Maybe Dean and Cas had been taken by surprise.

“No,” said Dean. “That’s the freaky thing. We were downstairs, talking to his wife. When I started to ask about those scars on his arms she started acting pretty cagey and I realised something was up; but just as I was going for my weapon, there was this yell from upstairs. You know. You can tell when something’s dying. By the time I got up here, well… the guy was a cranium short.”

“Huh,” Sam said, forehead wrinkling in puzzlement. “And where is the, uh, cranium now?”

“Well…” said Dean. “You got me. It seems to have disappeared. Guess you could say he lost his head.” He beamed.

Now this, Sam didn’t like. Not Dean’s joke – although that was bad enough – but the circumstances of Abraham’s demise. Sure, he was grateful that the guy had been helpfully slaughtered before he could make any serious trouble for Dean and Cas; but an inexplicable decapitation was almost never good news. Especially with what had happened just last month.

He looked up to meet Dean’s eyes. As usual, they were on the same track.

“I know, bro. Arkansas all over again.”

It had happened while they’d been after a particularly vicious werewolf in Malvern, a tricky hunt which had left them chasing their tails for days while the body count just kept climbing. But when the three of them had put the pieces together – Dean’s thoughts unexpectedly jogged by a misunderstanding from Cas – they’d found their culprit already dead, her corpse gruesome and headless on her blood-spattered living room floor. They’d assumed another hunter had beaten them to it: but looking at Abraham’s lifeless body, the connection seemed all too clear.

“What do you think’s going on? A hunter wouldn’t just leave him like this.”

“I don’t know, man. I’m starting to worry.”

“Well, you and me both.” Sam looked around. “Where’s Cas? Maybe he has some ideas.”

Castiel turned out to be in the kitchen downstairs, cooing over his guinea pig. Sam tried to engage him in discussion about the mystery killing: could it be a rogue angel trying to do some good? Cas thought not: decapitation wasn’t an angel technique. But he barely looked at Sam when he said it. Instead, he crouched by the kitchen counter, peering into Muriel’s eyes.

“She is in distress,” Cas said. He was right: the little creature looked upset, trembling and squeaking under Castiel’s soothing fingers. “I believe her to have been traumatised by the events of this afternoon. The cry as the beast perished was quite alarming. Muriel has a very sensitive disposition.”

Dean, in the doorway, groaned and rolled his eyes. “I’d love to hear more about what a special little flower she is, but I’m starting to think we should leave. I’m pretty sure Mrs Abraham just called the cops. So let’s get on the road.”

They were fourteen hours into the journey, Sam driving, when he heard a small sound of dismay from the back seat.

“Cas?”

“My fears about Muriel’s mental state have been proven right.”

Sam waited.

“Unfortunately, she has relieved herself. Quite profusely. All over the seat.”

Sam looked across at Dean, sleeping against the window. However helpful she’d been with this case, he didn’t think Muriel would be coming out hunting again.

~*~*~*~*~*~*~

“Cas, Kevin is basically an infant genius. I’m pretty sure he’s capable of looking after one overweight rodent.”

Sam watched two blue eyes narrow in annoyance as Castiel tugged his trenchcoat tight around his body, refusing even to acknowledge what Dean had said. Cas had been in a bad mood for the duration of the hunt: a relatively straightforward salt and burn in Colorado, complicated only by a lost (and haunted) false nail and, best of all, with no decapitations to disturb them. Half-guiltily, Sam had found himself enjoying it. Eating at grubby diners and sharing a threadbare room, bickering with Dean about music and films and TV, it had felt like the days when they first started hunting together: like the alienation of the last few years was finally clearing away.

Castiel, on the other hand, seemed unwilling to get over Dean’s refusal to let Muriel back in the car. Sam wasn’t sure what his friend had expected: if you knew Dean, you knew that you couldn’t mess with his baby. But Cas didn’t seem to have processed that memo, and there’d been a truly spectacular showdown on the road outside the bunker when he strode out to join them with the guinea pig firmly in hand. Sam hadn’t seen Dean so completely dumbfounded since the day they’d discovered the Batcave. He’d physically marched the angel back inside, not letting him out of the front door until Muriel was shuttered up safe in her hutch. And now, four days later, Cas was still sullen and sulking.

“Seriously, Cas,” Sam said. “If you can’t cope without her then maybe you should stay home next time.”

“Don’t be absurd,” said Castiel. “I am a hunter now. I must hunt. The proper solution might be to procure my own vehicle.”

“If you want to go solo,” Dean said, “that’s fine. Just _don’t_ expect me to let your incontinent guinea pig into my ride.” He leant over and cranked the music loud.

Sam shook his head, amused. He liked Muriel just fine, but Castiel’s passionate attachment seemed a little excessive. Apparently his human emotions were still calibrating.

It was late by the time they finally arrived back home; so Sam wasn’t surprised to open the door onto darkness. Kevin must have gone to bed. He was, however, startled when his click of the light switch triggered a noisy response on the far side of the room, sending something heavy whizzing over the ceiling towards him. With his reaction speed still a few notches slower than normal, Sam was grateful for the firm tug of Dean’s hand on his jacket, pulling him back and out of the way as the object clanged violently into the wall where he’d just been standing. Sam inspected it. A cauldron, loaded with cutlery, strung onto a makeshift zipline: a trap.

Dean pushed past him to lean over the balcony. “Kevin!” he yelled.

Kevin’s pale face peeped timidly into the room. His hair was clumpy, sticking up in all directions, and there was a familiar grey to the skin underneath his eyes. Apparently, he hadn’t been sleeping. Again.

“What is this?” Dean asked. “ _Home Alone?_ ”

“Sorry,” said Kevin, emerging slowly into the doorway. Sam could see the glint of metal from behind his back. “Things got kind of weird while you were away. Come down and I’ll tell you all about it. But – er – you probably want to be careful how you go on the stairs.” Kevin’s gestures revealed the weapon that he was holding: a substantial battle-axe Sam thought he might recognise from a suit of armour Dean had once tried to try on. Kevin pointed the weapon towards Dean’s feet. “Don’t tread on the fifth one. Or the thirteenth. Or the twenty-first.”

“What…?”

Kevin looked cagey. “Just taking precautions.”

Sam hopped carefully down the staircase behind his brother before collapsing gratefully into the comfort of a library chair.

Dean looked at him with concern. “I’m gonna go make some coffee. Sammy, you good?”

Sam smiled up at him. “I’m fine, Dean. Just a little worn out.”

Dean pursed his lips, but didn’t complain.

By the time his brother had returned from the kitchen, Sam was laughing as Kevin dismantled his traps around him, balancing on top of a bookcase to unhook a bucket from over the door. “I don’t know whether to be impressed by your creativity or worried that I’m gonna get caught out by something you forgot,” Sam said. He didn’t voice the third option, quiet at the back of his mind: to mourn the fact that this was what Kevin had become, the swotty little kid with his plans for university harried into a constant state of nervous paranoia. But really, what could you do? These were the costs of the job.

Dean leant over, placing two mugs on the table. “If you’ve messed with my bedroom, Kevin, we’re going to have a serious issue.”

Kevin giggled, half-nervously, keeping his eyes on Dean’s face. His brother’s expression was grim, but Sam recognised the light in his eye that said he was messing, tormenting Kevin deliberately as he’d used to love doing with Sam. This was what Sam liked about having Kevin and Cas in the bunker. They helped to readjust the family dynamic: Castiel’s cluelessness and Kevin’s youth giving Dean a new target for his grumpy old man persona, opening up a welcome new big-brotherly space for Sam. It helped relieve the strain of what at tenser times could be a stifling sibling relationship. More people, Sam thought. More friends. This was healthy and good.

“No, nothing in your bedroom, dude. It’s just the main room,” Kevin said. “Mostly.”

“Anyway,” said Sam. “Now we’re all here, you can tell us what happened.”

“Well. Everything was fine for the first couple of days,” Kevin said. “You know, just me and Muriel, reading the angel tablet, watching TV. So on Tuesday evening we’re catching up on _Orange is the New Black_ ; popcorn for me, radish for Muriel, everybody’s happy. But then there was this terrible noise from out front. It sounded like somebody was trying to break in. You know, all this banging, shouting, it was pretty scary.”

“What were they saying?” Sam asked.

Kevin scratched at his chin. “I think they were after Castiel.” He made an apologetic face in Cas’s direction. “It sounded like, you know, angel stuff.”

“Angel stuff?” Sam was surprised to hear Dean’s voice so panicked and gruff. Wasn’t it always angel stuff? But his brother seemed unusually disturbed by Kevin’s story, gripping his hands so tightly together that Sam could see the skin turn white.

Cas was quiet in his chair in the corner, running his fingernails through the fur behind Muriel’s ears. “I have caused a great deal of difficulty in heaven,” he said. “I suppose it is not surprising that my fallen brothers should seek revenge.”

“But no,” Dean said, “they shouldn’t be coming here. How did they find you? I thought the bunker was safe.”

Sam said, “We haven’t exactly been careful. You know, Cas will come into town with me on the grocery run or whatever. And we don’t know who’s an angel any more. It only takes one guy to find him and follow us home.”

Dean slammed an emphatic hand on the edge of the table. “This is serious shit, Sam! What if they talked to each other? We could have a friggin’ angel army at our door!”

“If you’ll let me finish,” Kevin said, “I’m pretty sure these guys aren’t going to be talking to anybody.”

“What happened?” Sam asked.

“So, I hid out downstairs for as long as I could, hoping and waiting for them to go away. And you know, eventually it did go quiet. I guess they decided they had the wrong place. So I left it a little longer, just to be safe.” Sam wondered how many hours of terror the innocuous phrase might be hiding. “Then I went upstairs and… dude. Somebody killed them. Like, full on chopped off their heads and left them lying on the ground out back.”

“ _What?”_ Dean was doing that thing where he was so worried that it came out angry. Sam knew this reaction from a lifetime on the road with his brother, but he could see both Kevin and Cas shift anxiously at Dean’s changing tone.

“It’s okay, Dean,” Sam said. “Kevin… where are the bodies?”

Kevin looked embarrassed. “I already salted and burned them. Isn’t that what I was supposed to do? I didn’t want anybody else to come by and start busting my ass about the two headless corpses on the doorstep.”

“No, no, you’re right,” Sam said. “Good point.” He looked at Dean. “It’s got to be related, right?”

“Related to what?” Kevin said, puckering his face in concern. Sam’s account of the recent, gory developments didn’t help. With every further detail, Kevin sank deeper in gloom. By the time Sam finished he was positively saturated with woe. “So, what, now we’re all being stalked by some ghostly headhunter?”

“I guess _maybe_ ,” Sam said. “But it doesn’t make much sense. Why follow us on the last two hunts and then turn up at the bunker, when we’re not here? Plus, it doesn’t seem to be angry, not with us. It’s killing the things we’re fighting when they’re trying to _hurt_ us.”

Cas said, “I’m just glad Muriel is safe.” He stood up and lifted her out of his lap, setting her down on the golden wood of the table. She skittered over towards one of the central lamps, her whiskers quivering and her eyes very black.

Everybody watched her.

In the end it was Sam who said it. “Yes. Muriel _is_ safe. And Muriel was safe when she was with us on the last few hunts. In fact, Muriel’s been kept _extremely_ safe ever since she got here.”

“Indeed,” said Castiel modestly, “I’ve been a conscientious caregiver. My years of experience guarding Dean have proven excellent preparation for the role.”

There was an awkward pause before Dean said, “I think you’re missing the point. Don’t you think it’s a little strange: the one time Powder Puff here stays home, this headless… hoodoo… magic, or whatever it is, starts operating right here in Lebanon?”

A scandalised expression spread slowly over Castiel’s face. “Are you trying to insinuate that Muriel is in some way responsible for violently murdering two of my kin?”

“All I am saying,” said Dean, “is that it wouldn’t be the worst thing she’s done.”

Cas’s jaw jutted forward and his eyebrows drew together. When he spoke, it was in the deeper tone he reserved for moments of crisis: the voice which reminded Sam that the guy he usually thought of as their quirky little friend had spent something close to eternity as a top-level heaven-trained soldier. “Your attitude is grossly unjust. I have heard quite enough for one night. I think, at this juncture, Muriel and I will retire.”

Sam, Dean and Kevin watched as he tucked the guinea pig under his arm, stalking out of the library with his back stiff and his head held high. “Seriously,” Dean said, “he is _way_ too close to that animal.”

“I guess you might say they share a profound bond,” Sam said. He looked at Dean. “Regretting our purchase, are we?”

Dean frowned. “What are you talking about?”

“You know. You must be having second thoughts about buying Muriel in the first place. God knows you two don’t get along.”

“Sammy? Are you sure… I didn’t buy her. You did.”

“Uh… I really didn’t, Dean.”

Three heads swivelled back towards the door through which Cas had just left.


	2. Chapter 2

By the time Dean got up the next day, grabbing a cold slice of pie from the fridge, Sam and Kevin were elbow-deep in books, folders and dust. Both of their hands were grimy with the dirt of long-unopened pages; and the generous garlanding of cobwebs through Sam’s messy hair attested a morning expedition deep into the bunker’s interior. Underneath the table, Castiel was constructing an elaborate house for Muriel out of the empty archive boxes they’d rejected.

Sam looked up. “So, get this. Cas has no idea where Muriel comes from. She just turned up outside his room one day.”

“Jeez, Cas,” said Dean, “and you didn’t think to mention it?”

“I assumed,” Castiel said haughtily, “that she was a birthday present from one of you.”

Dean digested this. “Do you actually  _have_ a birthday?”

“One might consider my recent transition into full humanity a kind of rebirth.”

“Well. A very happy rebirthday to you,” Dean said. “But… we don’t tend to go in for that kind of thing, much, around here.” A grim expression flitted across Sam’s face. Dean wondered what was going through his brother’s mind. Sammy certainly wouldn’t be short a bad birthday memory or five.

“Yeah. Not a birthday gift,” Sam said finally. “But we still have to work out exactly what she  _is_. So… Kevin and I have a number of theories. Possibility one: Muriel’s some kind of shape-shifter. Maybe something like Portia, the dog-woman, you remember?”

Dean turned to Cas. “Muriel ever turn into a hot chick when we’re not around?” He regarded the guinea pig critically. “Or, you know, a little old lady?”

Cas glowered. “No. Muriel has shown no evidence of a human form.”

“Doesn’t prove anything,” said Sam. “Peter Pettigrew held out for  _years._ ”

Kevin laughed. “Yes, Cas. Muriel is the Scabbers to your Ron.”

“I don’t know what you mean,” said Castiel. “Muriel has never suffered any kind of skin condition.”

“Moving on,” Sam said, “there’s a spell here which forces an animagus to reveal its true form. So I’m thinking maybe we should start with that.”

“Sounds good to me,” said Dean. “What do we need?”

~*~*~*~*~*~

Two hours later, Dean emerged triumphantly into the map room, brandishing a small, dusty bottle in his hand. “Guess who just found the powdered oryx horn?”

“Oh, great,” said Sam, looking round from a jumbled heap of ingredients. “I think that’s the last of it. Kevin, can you go and get Cas?”

Dean strode over to where his brother was standing, a book open before him on the central table. “This looks complicated,” he said.

“It is,” said Sam. “If you have to do this spell on an animagus, the assumption is that it doesn’t want to change. So you have to get it under your power initially, and then there’s a second part which is the actual transfiguration. Plus, the whole spell is in this weird Romany dialect and I’m not totally sure on the pronunciation. I mean, I can read it fine but I’m not sure about saying it out loud.”

“You guys will be great,” Dean said. “You and Kevin? That’s like 300 points of IQ right there.”

Sam gave an uncertain huff of thanks. “Well, none of it’s going to work if Cas won’t hand her over.”

Eventually, Cas did: though he was mulish and resistant to the last. Clucking in annoyance at Sam’s too-confident handling of his pet, he insisted on seating himself right next to the ceremonial circle. He reached towards Muriel so many times that Kevin ended up slapping his hand away before jerking back, his face evincing horror at his own audacity. Sam gave him a reassuring grin.

“Kevin’s right, Cas. The sooner we can get going, the sooner you and Muriel can go back to playing house.”

But as it turned out, Cas might as well have resisted. Sam read the whole spell through twice over, enunciating every word with an exaggerated stretch of his mouth. Dean and Kevin supervised one another over the blended ingredients, contaminating Dean’s brand-new measuring spoons as they balanced proportions of eagle and falcon blood. And yet, after forty minutes of meticulous incantation, Muriel remained resolutely in guinea pig form.

“I don’t think she’s changing,” said Dean.

Sam sighed. “I suppose first time lucky was too much to hope for. Don’t worry, we’ve got some more ideas on hand.”

But several hours later, five ideas down the list, Muriel’s secrets were still very much her own. Dean looked around the room. Kevin, bored, was swinging on the legs of his chair, flicking through a dark-covered leather-bound book. Sam was hunched over another heavy volume, chewing thoughtfully on the knuckle of his thumb. And Castiel was back under the table, guiding Muriel through a cardboard labyrinth. Dean crouched down, joining him on the floor.

“Maybe,” said Castiel, “we should try to locate an angel.”

Dean sat upright with a jerk, smacking his head painfully against the underside of the table. “What’s that?”

“An angel would be able to speak with Muriel. It would be easy for them to ascertain the truth of her origin.”

“Uh… Run that past me again?”

“Oh, Dean. Don’t you recall the case we worked in Oklahoma? I think you’ll remember my interrogation of a suspicious feline.”

“Dude. That was cartoon crazy-town. I thought it was a special case. Are you telling me you guys are all Dr Doolittle, all the time?”

“You are all God’s creatures, Dean.”

Cas watched as Dean’s brow furrowed in thought. This was a new idea and it needed some consideration. “I don’t think summoning any more angels is a good idea. Remember what Kevin said? They wanted to kill you, dude.”

“I agree.” Kevin’s voice floated down. “I don’t want to see any more angels for a while. No offence, Cas. I say we keep looking.”

“Sure,” Dean said. “You get on it. I’m going to make lunch.”

~*~*~*~*~*~

Sam looked up from his plate of chicken salad. “Dude, stop watching me like that.”

Dean blinked. “I’m not watching you. And anyway, I’m just checking you’re eating your greens.”

Sam curled a sceptical eyebrow. “Since when do you have to check on my nutritional intake? Wait, don’t answer that. Since the trials. I know. But seriously, man, I’ve been back on my food for months. I’m getting there. You don’t have to baby me.”

“I know,” said Dean. “I know.”

“Sometimes I feel like the friggin’ guinea pig, that’s all. I mean…” Sam gestured over to where Castiel was hovering, feeding lettuce to Muriel leaf by leaf. “Look familiar to you?”

The corners of Dean’s mouth twisted in a grimace of amusement. “Bet Cas would like to braid ribbon into your hair, too.”

Sam held up his hands. “Don’t get me involved in that.”

“But seriously,” and a strange, almost hunted expression shot over Dean’s face, “this guinea pig. Do you… I mean… you know how you space out sometimes, lately?”

Sam frowned. “Yeah.”

“Has that ever happened when you and Muriel were… alone?”

“I don’t think so. What are you worried about, that she took advantage of me?! I might not be on top form, Dean, but I think I can handle myself against a six-inch rodent.”

“No, no, I know, but… I mean, we don’t know if she’s  _just_  a six-inch rodent.”

“So, what, you think she’s violating me in my sleep? Or… whatever it is? Seems a little unlikely, wouldn’t you say?”

“Just forget it, man,” Dean said. But Sam could see that his brother wasn’t at ease. He darted little glances at Muriel throughout the meal, shifting into a positive glare when Cas left the table for a second helping. Something about the guinea pig was seriously getting to Dean.

The thing was that really, Sam agreed. It couldn’t be good to have something unknown just living amongst them unchecked. Even Muriel, nestling innocent against the mustard, might turn against them at any moment. It was time to get back to the books.

~*~*~*~*~*~

“OK,” Sam said, “What about this one? She might not be an animagus but she could still be something  _like_  a familiar. This spell should be able to conjure an image of whoever or whatever she belongs to.”

Cas objected. “She belongs to me, now.”

“I don’t know, Cas,” said Sam, gently. “I know you’ve been looking after her but it’s only been six weeks. Whoever she originally belonged to might have had her for years.” He looked at Dean. “They could be missing her.”

But that spell went the way of the others, Sam and Kevin carefully chanting a complicated, syncopated incantation while Dean lit fires in a series of small bowls around the circumference of the symbols that Sam had chalked out. The air in the bunker hung dense with herb-scented smoke; but the clouds stubbornly failed to resolve into a readable image.

“Come on, dude!” Dean said, in the end, frustrated. “Really. Come on. Could you give us a break?”

Muriel gazed steadily up at him. “Meep,” she said.

~*~*~*~*~*~

“It’s getting late,” said Dean, looking at his brother. Sam was really flagging now, drooping quietly over the papers on the table. Kevin still bobbed anxiously around the bookshelves; but Dean was pretty sure that since making their acquaintance, the kid had consumed enough over-the-counter pep pills to keep him going for the next thirty-some years. And Castiel, still not used to the limitations of full humanity, had nodded off in an armchair hours before. Muriel was dozing on his thigh. Dean glowered at her, the cause of all this trouble, the reason Sammy still wasn’t tucked up and sleeping.

“Hang on,” Sam said wearily. “I’ve got one more idea.”

“OK,” said Dean. “But then, bed.”

“So, it’s not exactly a solution in itself. But there’s a charm here that should show if somebody’s possessed.”

“We already tested her,” said Dean. None of them had been sure if a demon could actually possess an animal, but a little sprinkle of holy water was easy and quick to apply. Muriel hadn’t been impressed with the impromptu bath – and, as Dean had pointed out, her eyes had been black to start with – but she certainly hadn’t seemed to be in pain; so they’d ruled out that option, just like all of the others they’d tried.

“Yeah, I know,” Sam said: “but this doesn’t just work for demons, it should be anything, any kind of supernatural or foreign force. I think it’s pretty straightforward, just a few sigils on the floor, sit her on top of them, say these words and if there’s something strange inside her then she should start to glow.”

“ _Anything_  supernatural inside her?”

“To glow, I know – hey, what?” Sam blinked. “I didn’t think that was the bit you’d have trouble with. Yeah, anything. You know, spirits, um, witches, anything that can get inside and control a person. Or a guinea pig, I guess.”

“Like, for example,” and the pitch of Dean’s voice was rising, “angels? Say?”

Sam looked at his brother, curious. “You’re really bothered about him, aren’t you?”

Dean froze. “About who?”

“About Castiel. You seem so worried about the angels. It’s nice. I mean, I guess I’m worried too, if he’s such a target as he seems to be. But it’s OK. He’s here with us. He’s safe. And I’m fairly sure that even with a shortage of vessels, there’s not an angel out there desperate enough to want inside a guinea pig. Can animals even give consent?”

Dean’s eyes narrowed thoughtfully before he spoke again. “Yeah. Yeah, I am worried. About Cas. I think… we should probably look into some other options. You know. To be safe.”

“What?” Sam was incredulous. “There’s like, no chance it’s an angel inside Muriel. But it  _could_ be something else and we should at least rule it out.”

“I said no, OK? Look, it’s way too late. Let’s just go to bed. All right?”

“What? Five minutes ago you said this would be fine! You have to stop babying me, OK? I’m not much of a hunter if I can’t even handle a day of research without passing out.”

“Sammy. I’m not trying to criticise or to doubt your, I don’t know, your manhood or whatever. I’m just saying that I think we’d all be more effective if we got some sleep.”

Sam opened his mouth to make another outraged comment – but his treacherous body turned the movement into a yawn. When he reopened his eyes Dean was smirking complacently, an unspoken ‘I told you so’ hanging pointedly in the air. Sam thought about it. Truth told, he was pretty much beat. And hopefully by morning, Dean would have gotten over whatever was bothering him. He needed to see that Castiel was fine with them, where he was. Of course, Cas was mourning the loss of his grace: but every day he seemed a little closer to mastering the art of humanity. Even if his common sense and his hunting skills were both still very much in development.

“Alright,” Sam told his brother. “But this doesn’t mean you’ve won.”

“Dude,” Dean said. “You forget. I  _always_  win.”

~*~*~*~*~*~

Dean checked his watch for what felt like the fiftieth time. Two-thirty. At least ninety minutes since Sam went to bed. Surely that was enough time for even his light-sleeping little brother to be safely off in the land of nod?

Barefoot and cautious, Dean creaked open the door of his room and tiptoed softly down the corridor. Cas and Kevin were in bedrooms way down round the corner; Sam’s door was the only one that he had to pass. Dean paused, holding his breath, as he reached it. If he listened hard he could hear Sam’s wheezy breathing, evidence that his lungs still weren’t back up to speed. In. Out. In. Out. It was so slow that Sam had to be sleeping. Feeling more confident, Dean pattered on towards the bunker’s central hub.

With Muriel’s loyalties and identity in doubt, Sam and Kevin had succeeded in pressuring Cas to move her out of his room. Dean had never been happy with that arrangement – it just wasn’t sanitary, he thought – but now he was especially grateful for Cas’s change of heart. A  _Mission Impossible_  air-vent raid past a sleeping Cas’s bed wasn’t really the way he’d like to spend his Wednesday night. Instead, he had ready access to the guinea pig in her new location under the entryway stairs. Unwilling to turn on the lights (there was a central system he hadn’t yet mastered, and he could do without waking Sam up), Dean followed the thin blue beam of his torch over to where Muriel was scrabbling in the straw of her hutch.

He slid open the latch, swung wide the door and reached back into the box. Great. The guinea pig had pressed herself right against the back wall, cowering away from his hands.

"Come on,” hissed Dean. “I’m not gonna hurt you. Just wanna find out exactly what’s got into you.”

He squatted down on a level with the hutch, reaching his arm in all the way until he felt the soft brush of fur across his fingers. “Heeeere guinea guinea guinea,” he crooned.

Suddenly, silently, with no warning or expectation, the cold chill of a blade touched a shiver across his neck.

“Step away from the guinea pig,” said a rasping voice.

~*~*~*~*~*~*~

Sam opened his eyes, flicking a cautious glance around the room. For a moment, he didn’t move. Something was wrong. Some tiny shift in the atmosphere, some infinitesimal noise, had woken him: and though his room was clear, he could feel his nerves buzzing with the absolute certainty that there was a hostile intruder close by. Hurriedly, he pulled on a T-shirt and jeans, slotting his gun into the waistband against his back. The corridor was dark. A light glimmered from the central room. Careful, quiet, Sam crept slowly up to the door.

“Leave me alone, you crazy bitch!” Dean said. Then, a muffled cry; like a hand had clamped over his mouth.

Defensive instincts flaring, Sam moved hesitantly forward, poised on the balls of his feet. From this position he could see only the nearest corner of the library. The lights were blazing and Dean’s legs were in evidence, bowed wide across a table where someone had apparently tied him down. Sam could see the shadow of a monstrous figure on the wall: something huge, much bigger than a man, bending over his brother. Sam stepped through into the next room, pressing himself against the wall to keep out of the way. Reaching the pillars of the library door, he paused for a moment before cautiously angling his head to look in.

He had been right about Dean’s position. His brother was spread-eagled across one of the tables, limbs trussed to the corners and rope now twisted tight over his mouth. Stalking around him, slow and menacing, was the monster whose shadow Sam had seen. It was probably nine feet tall, with leathery wings folded behind its back and crab-like claws sticking menacingly out at its sides. Coils of dark hair hung at its temples. But what Sam was most concerned about was the weapon it carried, a fearsome knife whose serrated edge glinted a threat in the lamplight. As Sam watched, the monster ran the tip across Dean’s chest, puckering the fabric of his brother’s grey T-shirt.

A woman stood at the second table, behind the one to which Dean was bound. Olive-skinned and dark-haired, she wore a patterned gold and brown gown which fell to her sandalled feet. Her face was narrow and her features strong, their heavy bones accentuated by the lustre of her metallic headdress. Necklaces hung in thick ropes around her neck; and the deep copper bowl on the table before her suggested a ritual in process. A priestess, Sam thought. An ancient priestess. She seemed at once very old and very vivid and young.

She looked towards the doorway. “Come out,” she said.

Huh. Sam’s cover had been less complete than he’d hoped. Well, here went nothing. Drawing himself up to his full height, he walked into the room, taking his gun from the back of his pants as he walked. Recognising Sam’s footsteps, though he couldn’t move his head to see him, Dean closed his eyes in what might have been despair, or relief.

“Let my brother go,” Sam said.

The woman – the priestess – laughed. “I don’t see why I should. I need him. Or, I need his blood.”

Sam looked again at the monster, pacing evenly around the table before him. His entrance hadn’t disturbed its steady tread; it barely seemed to notice that he was there. Instead, its eyes were fixed on Dean, the knife drawn out again and again to play against the lines of his body. Sam wasn’t sure that he could take it down in time. Sure, he could move fast enough to shoot it: but who knew how much effect a bullet was likely to have?

“He could be dead in a moment,” the priestess said. “My friend here is more than capable of the task. As your experiences in the last few weeks can attest.”

“That was you?” Sam asked.

The priestess gestured at the monster, her bracelets clashing. “It was the decapitator. I sent him to guard my prize.”

Sam glanced down at Dean’s face. His brother’s carefully maintained expression of stoicism was betrayed by a stubborn twitching in the muscle along his jaw. Dean was angry, and scared.

“What do you want?” Sam asked.

“I’m here to retrieve my possession,” the woman said, indicating the copper bowl with a flick of her elegant fingers. “Mine. Buried, with  _me_ , for the afterlife. And  _taken_  from my tomb by some barbaric archaeologist to file in the collection of stolen exotica of which you seem to be the custodians.”

“You’ve come here to get your  _bowl_  back?”

The priestess curled her upper lip in a sneer. “The bowl is already mine. As is the guinea pig who is sitting inside it.”

Sam looked over. Right on cue, a small ginger face emerged from the rim of the vessel, ears twitching like they were listening to what was said. Of course, Sam thought. Muriel. He should have guessed.

“Surely you might have realised,” said the priestess. “Your spell to summon her owner was what brought me here.”

“That was supposed to  _show_ you to us,” Sam said. “An image of you. This, the whole human sacrifice thing, wasn’t exactly what we ordered.”

She smiled. “Unfortunately, my long residence in the afterlife had weakened me to the extent that I could send out my familiar spirit, but not myself. He has been protecting the creature since she returned. But the energy transmitted by your spell was sufficient to help me break through at last.”

“… To retrieve your guinea pig. Right. Well, correct me if I’m wrong; but you’ve got her right there. Where does roping my brother to the table come into it?”

“Some more spellwork is necessary. The same power that has reanimated the creature – that reawakened her lifeforce and alerted me to her presence – some person must have had a powerful need for companionship. And so the ownership has… temporarily… transferred.”

“So… she’s not actually yours at all.”

The priestess raised her chin, lips set tight and eyes gleaming green danger. “ _She is promised to me,_ the proper reward of my lifetime of temple service, the status symbol of a true Moche priestess. How dare you demean my achievements and my power by suggesting that she might be so easily lost? This is merely a terrible mischance, the product of a thieving culture which systematically ransacks the tombs of the dead. How should the magic of an animal like this understand the complexities of your new barbarism?  _The guinea pig is mine_.”

Sam stepped back, his hands raised defensive before him. “Sure. Sure. OK. And you need the blood… why?”

“The blood of the vanquished enemy contains great power. Drinking it will permit me to reclaim my companion. And then I will leave.”

“So you already have the juice to get back home?” The priestess gave a slow, stately nod. Sam exhaled. OK. This would be OK. He flickered his eyes towards Dean, squirming and impatient under the circling knife. “Well, before you start chowing down on my brother’s B positive… Maybe we could arrange a swap?”

“You would be willing to give up your claim to her care?”

“For Dean?” said Sam. “Yes. I would give up the guinea pig, for Dean. So go on. Go for it. Take her away. Get lost.”

Bending with a spell on her lips, the priestess curled her fingers around Muriel’s middle. Muriel squeaked. Disappointed, the priestess set her back down.

“It has not worked. She does not belong to you.”

“Oh,” Sam realised. “Cas.”

A noise that sounded exasperated escaped from the edge of Dean’s mouth.

“Sorry, Dean,” Sam said. “I’ll be back in a minute. Just… stay there.”

Another noise, louder than the first. OK, Sam thought. He’d probably deserved that one.

~*~*~*~*~*~

Dean strained his limbs against the priestess’s ropes, mentally cursing Muriel with every bad word he could find. He’d always known that thing was a bundle of trouble. He should have made Cas get rid of it the  _minute_  it had messed up his car.

And with that thought, at last, he heard two pairs of footsteps approach. Tugging upright as far as he could, he caught his brother and his friend at the edge of his vision. Cas was shuffling slowly on slippered feet, crumpled and dozy, his eyes hooded with sleep. Sam hovered impatiently behind him, a mother hen pushing her chick. Dean watched Cas’s gaze pan around the room. He blinked at Dean on the table, rubbed his eyes with his hands, and then jolted suddenly into wakefulness at the sight of something over Dean’s head. Must be the godforsaken animal, Dean supposed.

“Give her back to me,” Castiel croaked. “She is mine.” Oh, great, Dean thought. Nice work on the explanations, Sam.

But then, “About that, Cas?” said Sam. “This nice lady here has come all the way from…”

“Peru.”

“She’s come all the way from Peru, from ancient Peru actually, to get her guinea pig back.”

“Oh,” said Cas. “I see.”

“So what would be really good is for you to just say that you don’t mind, that you revoke all your rights to Muriel” – he paused, for a confirmation that Dean couldn’t see – “and that you are happy for her to take her with. Into, what, into the afterlife? Yeah. Does that sound OK?”

Cas looked at Dean. “I suppose if I refuse then Dean will be brutally murdered?”

Sam considered. “It might not be brutal.”

Cas shifted his gaze to the decapitator. “I am certain it will.”

On the table, Dean gave an outraged bleat.

The priestess spoke. “Do not trifle with me. If you continue to refuse to surrender your ownership, I will be forced to use – Dean’s – blood to take control of Akllasumaq myself.”

“Her name,” said Castiel stonily, “is Muriel.”

“Let’s not worry about the details,” said Sam. “Come on, Castiel. Please. Let’s get this done.”

“But Sam. Muriel is my  _friend.”_

Sam paused for a moment, unsure about this development. “Dude. Dean is your friend too. I am your friend. You don’t  _need_  a guinea pig for companionship. Seriously. Look around you. Me, Dean, even Kevin and the stupid TV shows you guys like to watch. Muriel is nice, I’m sure, she’s a great guinea pig but she is  _just a pet_. Come on, please, man. It’s Dean. Look, if it makes you feel better then you can even, you know, braid my hair or whatever it is you like to do with her. I’ll watch  _Next Top Model_  with you.  _Dean_  will watch  _Next Top Model_. – Shut up, Dean. – Whatever it takes. Please, Cas, this should be straightforward. This is easy.”

Castiel looked at Dean; looked at the guinea pig. A heavy thoughtfulness settled on his face. His fingers twisted anxiously in the hem of his nightshirt. Dean could see Sammy, almost on tiptoes with strain, eyebrows working frantically as he willed Cas to make the choice. And then, finally, Cas turned his eyes back toward Sam.

“What do I have to do?”

“It is simple,” the priestess said. “You have merely to repeat these words.”

It wasn’t a language Sam knew: but vague memories of his class on early South American civilizations were telling him that few Moche texts had survived. Probably nobody had heard these words for hundreds of years. If he wasn’t so worried about Dean’s well-being, that might have given him a nerdy thrill. He might even be mentally cataloguing syllables to compare against modern dialects. Maybe. If he wasn’t so worried, that was.

Thankfully Castiel was less easily distracted, staring steadily at the priestess as he echoed her words. As the spell came to an end, she reached again into the bowl, clasping Muriel tight in her hands. “Thank you,” she said: and vanished, sudden and silent as Cas had once been.

Her bowl and her ropes disappeared with her; and Dean sat up, coughing, stretching his cramping limbs. “Thanks, Sam,” he said. “Maybe a little bit slow for my liking but, yeah, I’m glad you woke up.”

Sam looked at him. “We’ll talk about that later. Cas, are you doing OK?”

Cas’s whole body was slumped with dejection, all his usual perkiness now utterly drained from his face. He looked like a baby Sam after Dean confiscated his toys, trying to keep the tension down on a noisy car ride with Dad.

“Sorry, Cas,” Dean said. “Hell. You can get another guinea pig if you really want.”

Sam looked at him, quizzical, then directed his attention back to their friend. “Cas,” he said. “Are you all right? I didn’t realise that you were lonely, really lonely, like that.”

Cas looked up, tearful. “In Muriel, I found true companionship. Like that which you have with Dean.”

“Oh,” Sam said, unsure. “You know that you have companionship with us, though, right? That you’re part of the family here, too. It’s more than just me and Dean, now. Hey, Cas. You’re our third wheel.”

Something about the phrase seemed to work; Cas sniffed a couple of times and wiped his nose on his sleeve, resolving his features into an encouragingly cheerful cast.

“That’s it,” Sam said. Dean watched as his brother deflated, suddenly tired and wan. “I’m pretty exhausted, man. How are you doing?”

“Yeah. Yeah, I’m fine. You know me. Takes more than an undead Peruvian priestess and her monstrous decapitating pet to get me rattled.”

“Great. Excellent.” Sam closed his eyes. “I think I should go to bed. But maybe you could talk to Cas, make sure he’s OK? You’re probably the closest thing to –” and then Dean’s stomach flipped, as Sam’s shoulders stiffened, his face suddenly resettling into something rigid and strange. “These events were unacceptable,” Ezekiel said. Dean looked frantically over to Cas; but the angel had moved across the room to Muriel’s empty hutch, where he was sifting sadly through the abandoned remnants of straw.

“What?” Dean muttered, hushed and uncomfortable. “What events?”

“The invading presence of the angels the prophet described. The possibility of further heavenly spies. As I predicted, Castiel is a dangerous associate.”

“Come on, man,” Dean said. “You can’t make me kick him out now.”

Ezekiel’s eyes shone an angry blue. “Do you wish me to make my departure instead? Sam’s body is still profoundly damaged. I am certain he would not survive my loss.”

“OK, OK,” said Dean. “I get it.” A weight settled deep in his stomach. “Now can you at least get lost, before he overhears?”

“- a guinea pig he’s got, right now,” said Sam. “Dean?”

Dean blinked.

“Don’t look at me like that. You heard him. He practised for her on you.”

“Yeah,” Dean said. “Yeah. I know.”

“Good. I’m going to go and lie down.” Sam headed out of the room, patting Castiel’s shoulder goodnight.

Painfully conscious of his guiltily twisting insides, Dean forced himself over to join his friend. Cas turned to him with a determined expression of cheer, his fingers resting lightly on the lid of Muriel’s hutch. The sincerity that shone from his eyes hit Dean like a punch in the gut. “Thank you, Dean, for letting me into your home. Sam is right. I was wrong to think myself alone. I am truly fortunate to have found my new family here.”

Dean swallowed. “Yeah, Cas. About that,” he said.

**Notes for the Chapter:**

> This fic took me a bit outside my comfort zone (as you'll know if you've followed the rest of my stuff) so I'm a little nervous of posting it here... but I think it's kind of fun so, yeah, I'm going ahead!


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